To expand an operation area in which atomization of injected fuel is appropriately performed, improve combustion efficiency over a wide operation area, and reduce unburned components in exhaust gas.

Under quantitative control of an air flow rate by a sub throttle valve 90, air matching a requested air quantity is supplied to a sub intake supply port 75 not only during an idle operation but from an idle operation over an operation region in which the requested air quantity is less than a prescribed value, and when the operation area becomes one in which the requested air quantity is the prescribed value or more, a state in which the sub throttle valve 90 is opened is maintained, and an air quantity equivalent to the prescribed value is supplied to the sub intake supply port 75.

COPYRIGHT: (C)2011,JPO&INPIT